<> I usually run @ 50w into small amp and I see 13.7V on rcv and
<> 11.5 while xmit. If I run the power up to 100w, I see 13.7 and 10.8; do
<> I have a problem? I am using an unmetered Astron RS-35 into our standard
<> 220v house supply.
You definitely have a problem, Tom, but it has nothing to do with the power
supply you are using. You have excessive resistance somewhere in the DC
distribution between the power supply and the K3. Either your cable is
using conductors that are too small in diameter, the cable is too long, or
you have a loose connection somewhere. First of all, if you have any
connections such as a terminal strip or binding post, make sure that they
are screwed down tightly. Also check your solder or crimp connections.
The K3, like all 100W class rigs, will demand peak currents in the range of
20 amps. Distributing this amount of current without excessive voltage drop
takes care. I use an Astron 30A switcher here and have the nice and
convenient RigRunner type PowerPole distribution/fusing panels for most of
the equipment in the shack. But for the K3 power feed I go directly from
the power supply to the K3 with only 3 ft of AWG 10 cable, and only see a
couple tenths of a volt change from zero load to 100W CW key down. This is
what you should be aiming for if you want maximum performance from the rig.
I will take this opportunity to opine further, since this is an important
issue for me. Remote sensing is almost always used in industry when
delivering this amount of current over distances of two feet or more. It is
amazing that the amateur market has not used this simple and effective
solution. All it requires is a small twisted pair cable along side the DC
cable. I don't even think there are ANY power supplies marketed for amateur
use that include remote sensing capability! It would only add a couple
dollars to the cost.
Thinking in broader terms for the future, we are at or have exceeded the
technical capability of a nominal 12V input power system. It is time to
think about higher voltages for rigs used in the home environment, perhaps
48V. If there ever is a K4 (never say never, Wayne and Eric ;>), please
design for 200W with an internal or dedicated eternal Elecraft higher
voltage power supply!!!
73
... Craig AC0DS
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